The theme begins with a unique and defining strength of the Harvard-NIEHS Center for Environmental Health, the investigators' unmatched portfolio of population and patient studies of environmental exposures and their health effects. These studies of the real-world environmental exposures of human subjects ensure that Center research readily translates into public health policy and clinical practice. These population-based investigations combine with mechanistic laboratory studies to illuminate the pathways by which environmental exposures cause health effects. The Center makes this partnership a productive two-way street: Data from populations inform and guide studies of pathways in animal and cell culture models. In turn, the evidence from pathway studies is used to improve or develop new population studies of exposures and health effects. Together their Populations to Pathways research provides both estimates of human population risk as well as adding to the understanding of mechanistic pathways of environmental health effects. The investigations of populations and pathways in turn inform public health policy and clinical practice. To facilitate interactions the Center is organized around three Research Cores representing major cross-cutting environmental health exposures: Metals, Organic Chemicals, and Particulates. Each of the Research Cores has track record of productivity, potential for continued growth, and the ability to integrate and catalyze leadership in the future. Each Research Core is multidisciplinary and deploys the full range of our intellectual resources. These Research Cores have been highly effective in promoting integration and collaborations through seminars and symposium, invited speakers, working groups, and pilot projects. Each of the three Research Cores features toxicology, basic mechanisms, in vitro models, animal models, gene- environment interactions, epidemiology, risk analysis, risk communication and connects to the Community Outreach and Education Core. Each includes exposure assessment as well as health outcomes in both animal models and human populations. Moreover, each represents an area of considerable activity and accomplishment as well as a compelling list of unsolved concerns. By using the Center mechanism to increase integration, each Research Core is composed of individuals not only from a variety of disciplines, but also from a range of academic programs and departments throughout Harvard and at neighboring institutions. The Community Outreach and Education Core (COEC) provides a community context for the research and integrated health sciences occurring within the Center and supports the Center's goal to translate its research into public health policy and clinical practice, and serves as a conduit for the community and stakeholders to interact with and provide guidance to the Center in defining research priorities and opportunities.